2E13 is a scientific notation for the number 2 multiplied by 10 raised to the 13th power. This means 2E13 is equal to 20,000,000,000,000 (or 20 trillion). In this notation, "E" stands for "exponent," which is commonly used in mathematics and programming to represent large numbers.
One ampere is 1 coulomb (6.242×10^18) of electrons traveling past a point in 1 second. (2e13 / 1e-3) * (1 / 6.242e18) = 0.0032 or 3.2mA.
2 million are produced in the red bone marrow every second. 2 million are thus also killed in the spleen in order to keep the balance. The cells live for about 120 days so you have about 2E13 red blood cells in your body at one time.